linux-kernel - Re: current linux-2.6.git: cpusets completely broken

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Message-ID: <b647ffbd0807141921n13ffa59x416fc024c734ef02@mail.gmail.com>
Date:	Tue, 15 Jul 2008 04:21:10 +0200
From:	"Dmitry Adamushko" <dmitry.adamushko@...il.com>
To:	"Linus Torvalds" <torvalds@...ux-foundation.org>
Cc:	"Vegard Nossum" <vegard.nossum@...il.com>,
	"Paul Menage" <menage@...gle.com>,
	"Max Krasnyansky" <maxk@...lcomm.com>, "Paul Jackson" <pj@....com>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>, miaox@...fujitsu.com,
	rostedt@...dmis.org, "Thomas Gleixner" <tglx@...utronix.de>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Linux Kernel" <linux-kernel@...r.kernel.org>
Subject: Re: current linux-2.6.git: cpusets completely broken

2008/7/15 Linus Torvalds <torvalds@...ux-foundation.org>:
>
>
> On Tue, 15 Jul 2008, Dmitry Adamushko wrote:
>>
>> The 'synchronization' point occurs even earlier - when cpu_down() ->
>> __stop_machine_run() gets called (as I described in my previous mail).
>>
>> My point was that if it's ok to have a _delayed_ synchronization
>> point, having it not immediately after cpu_clear(cpu, cpu_active_map)
>> but when the "runqueue lock" is taken a bit later (as you pointed out
>> above) or __stop_machine_run() gets executed (which is a sync point,
>> scheduling-wise),
>>
>> then we can implement the proper synchronization (hotplugging vs.
>> task-migration) with cpu_online_map (no need for cpu_active_map).
>
> [ ... ]
>
> In particular, it should tell you that the code is too hard to follow, and
> too fragile, and a total mess.
>
> I do NOT understand why you seem to argue for being "subtle" and "clever",
> considering the history of this whole setup. Subtle and clever and complex
> is what got us to the crap situation.

Fair enough, agreed.


>
>                Linus
>

-- 
Best regards,
Dmitry Adamushko
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